Correction fluids are used for correcting handwritten, typewritten, photocopied, or laser printed markings on paper. Generally, correction fluids are applied to a paper surface in liquid form, and then allowed to dry to form a film which effectively covers erroneous markings on the surface and can receive a correct marking.
Water-based correction fluids, which are better for the environment than solvent based systems, typically include a pigment, e.g., titanium dioxide, and a latex binder, which is usually an aqueous polymer emulsion. Typical latex binder polymer emulsions are acrylic copolymers and ethylene vinyl acetate (EVA), which minimize the dissolution of underlying markings to which the fluid is applied, and imparts other advantageous properties to the fluid. Such dissolution of the markings causes so-called "bleeding" or "smudging" of the markings into the correction fluid, which causes a discoloration of the fluid film and corrected spot.
Although such water-based correction fluids based on emulsion polymer binders are effective on handwritten, typewritten, or photocopied markings, they do not prevent the problem of bleeding or smudging on all types of markings. For example, one type of marking that is difficult to cover with correction fluids without bleeding of the marking into the correction fluid is so-called "water-fast" ink, e.g., ball-point pen ink. Although these inks are referred to as water-fast, they contain a certain percentage of components, including dyes, that are water soluble. It is this water-soluble portion, i.e., about 5 to 15% of the water-fast inks, that causes the bleeding problem.
Although this type of ink has been widely used for many years, e.g., in so-called "stick" pens, of which over 3 billion are sold annually, the problem of bleeding or smudging of correction fluid when used to correct such markings persists.